Primary vs. Secondary Position

Dog Fight: Starship Edition FAQ primary vs secondary position

When a tier possesses only 1 card it is in "primary" position. There are some effects which allow for 2 cards to be set in a tier. When you can play more than 1 card into a tier this referred to as "Doubling Up". To double up you must play an effect/ability that specifically allows more than 1 action in a tier or states to place 2 cards in a tier.

When 2 cards exist in a tier the first to resolve is the "primary" card and the other is the "secondary" card. No player may have more than 2 cards in a single tier at the same time.

"Primary position" does not mean tier 1 and "secondary" position does not mean tier 2.

 You can see several cards designed to work with doubling up on the card database.